tripping is achieved. This requires a detection of the fault by an independent tripping zone 1.
To avoid sequential tripping as described, and when zone 1 is not available, weak-end infeed
tripping logic is used. The weak end infeed function only works together with permissive
overreach communication schemes as the carrier send signal must cover the hole line length.
The WEI function sends back (echoes) the received signal under the condition that no fault has
been detected on the weak-end by different fault detection elements (distance protection in
forward and reverse direction).
The WEI function can be extended to trip also the breaker in the weak side. The trip is achieved
when one or more phase voltages are low during an echo function.
In case of single-pole tripping, the phase voltages are used as phase selectors together with
the received signal CRLn.
Together with the blocking teleprotection scheme some limitations apply:
• Only the trip part of the function can be used together with the blocking scheme. It is not
possible to use the echo function to send the echo signal to the remote line IED. The echo
signal would block the operation of the distance protection at the remote line end and in
this way prevents the correct operation of a complete protection scheme.
• A separate direct intertrip channel must be arranged from remote end when a trip or
accelerated trip is given there. The intertrip receive signal is connect to input CRL.
• The WEI function shall be set to
WEI=Echo&Trip
. The WEI function block will then give
phase selection and trip the local breaker.
Avoid using WEI function at both line ends. It shall only be activated at the weak-end.
14.2.3 Setting guidelines
IP15024-1 v1
M13856-4 v5
The parameters for the current reversal logic and the weak-end infeed logic (WEI) function are
set via the local HMI or PCM600.
Common base IED values for primary current (
IBase
), primary voltage (
UBase
) and primary
power (
SBase
) are set in a Global base values for settings function GBASVAL.
GlobalBaseSel
: It is used to select a GBASVAL function for reference of base values.
14.2.3.1 Current reversal logic
M13856-6 v5
Set
CurrRev
to
On
to activate the function.
Set
tDelayRev
timer at the maximum reset time for the communication equipment that gives
the carrier receive (CRL) signal plus 30 ms. A minimum setting of 40 ms is recommended,
typical 60 ms.
A long
tDelayRev
setting increases security against unwanted tripping, but delay the fault
clearing in case of a fault developing from one line that evolves to the other one. The
probability of this type of fault is small. Therefore set
tDelayRev
with a good margin.
Set the pick-up delay
tPickUpRev
to <80% of the breaker operate time, but with a minimum of
20 ms.
14.2.3.2 Weak-end infeed logic
M13856-10 v6
Set
WEI
to
Echo
, to activate the weak-end infeed function with only echo function.
Set
WEI
to
Echo&Trip
to obtain echo with trip.
1MRK 511 358-UEN A Section 14
Scheme communication
349
Application manual
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